I checked the rear wheel and associated fixtures and fittings with a fine tooth comb and in addition to the coaster brake problem and a broken spoke... what do I find, but another broken spoke.

However this one is strange. Normally the spokes snap right along the outside (torque) edge of the drive sheave - all the ones I have had up to now have broken in that exact same place. This one has broken right at the very bottom where the flat goes into the hub flange plate - I dont know why it should have loaded up there since its as far away on the spoke from the torque moment and therefore thepoint of stress as it can be.

I have replaced both the spokes on the bike, and also checked things over. I will need a new mounting & bolt for the coaster brake and then I am good to go. I think I might have stressed it by using my body to brake the bike from speed as in over 750 odd miles I havent had a peep out of it until now and tonight was the only time I have used that method with the coaster.

Hi Jemma -- I think that you are talking about that little rinky dink bracket that holds the coaster brake arm in place -- the reason I call them rinky dink is for as important as they are - many just are not made to the highest standards !!!
You could probably make - bend one up from some better quality metal - with a good nut and bolt.
The spoke issue -- my new - fair quality MB mountainbike - broke a spoke on the rear a couple of weeks ago - same as your last - next to the hub - I didn't think that I had put it through that much of a test - but - who knows.
While at the local bicycle shop buying a spoke - owner said that they try to use Swiss spokes for replacement.
In the 70ess when I owned a bicycle shop - I don't remember spokes breaking on any of our new bicycles sold - unless misused -- HAS QUALITY OF SPOKES DROPPED ??
Ride That Thing - Mountainman

Those tiny brass washers might be useful for the average modern coaster brake. They're intended to take up some of the space in the bend of spokes, which are almost always intended for thicker flange aluminum hubs.

Do you run a front brake, JemmaUK? A coaster brake-only MB seems a risky thing to me. In addition, the extra strain directly put upon by a motor drive, and the extra speed may push the poor coaster to it's limits. A front brake, even a cheap aftermarket sidepull, is generally more effective than any rear brake, and redundancy can be a lifesaver should one fail.

I have used a pipe strap as a brake arm bracket in the past. Mostly because it was the only suitable thing I had. It is significantly thicker steel than the typical brake arm strap, and even has a rubber grommet to protect the chainstay finish. I don't remember where I got it exactly, but it was at a plumbing supply place.

Those tiny brass washers might be useful for the average modern coaster brake. They're intended to take up some of the space in the bend of spokes, which are almost always intended for thicker flange aluminum hubs.

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They might indeed do that, but the bike shop told me they use them to make sure the hub end of the spoke seats snugly into the hub hole, especially when re-spoking a older hub where the holes have expanded (or a cheaply made new one, they deliberately make the holes slightly larger than needed to facilitate machine assembly)